DOPPLER DIRECTION FINDER RADIO DIRECTION FINDER KIT Ramsey Electronics Model No. DDF1 Get in on the fun of radio direction finding (RDF) with this super kit ! The latest in affordable Doppler direction finding equipment available in a complete kit form ..this one even includes the receiving antenna. A must for the “fox hunter” at an unheard of price! • Elegant and cost effective design thanks to WA2EBY ! Featured in May / June 1999 QST Articles.
RAMSEY TRANSMITTER KITS • The “Cube” MicroStation Transmitter • FM25B Synthesized FM Stereo Transmitter • FM100B “Professional Quality” Stereo FM Transmitter • AM1, AM25 AM Transmitters RAMSEY RECEIVER KITS • FR1 FM Broadcast Receiver • AR1 Aircraft Band Receiver • SR1 Shortwave Receiver • AA7 Active Antenna • SC1 Shortwave Converter RAMSEY HOBBY KITS • SG7 Personal Speed Radar • SS70A Speech Scrambler • MX Series High Performance Mixer • MD3 Microwave Motion Detector • PICPRO Pic Chip Programmer • LC1 Indu
Ramsey Publication No. MDDF1 Price $5.00 INSTRUCTION MANUAL FOR DOPPLER RADIO DIRECTION FINDER TABLE OF CONTENTS Introduction to the DDF1 ............... 4 DDF1 Circuit Description .............. 4 Parts List ...................................... 11 DDF1 Assembly Steps ................. 14 Component Layout....................... 17 Schematic Diagram...................... 18 Initial Testing ................................ 22 Ramsey Warranty ........................ 23 RAMSEY ELECTRONICS, INC.
INTRODUCTION Radio direction finding is a fascinating hobby that has been becoming more and more popular in today's portable world. More recently, Doppler “df-ing” has become the rage, with a display that gives you a direct bearing on the location of the transmitter. Pretty neat trick considering you don’t need multiple separate receivers at different locations to triangulate on the mystery transmitter.
c = Speed of light We can calculate how fast the antenna must rotate in order to produce a given Doppler frequency shift with the following equation fr = dF x 1879.
The frequency of rotation is: fr = 500 x 1879.8/146 x 13.39 A rotation frequency of 480 Hz translates to 480 x 60 = 28,800 or almost 30,000 r/min, which pretty much rules out any ideas of mechanically rotating the antenna! Fortunately, Terrence Rogers, WA4BVY, proposed a clever method of electrically spinning the antenna that works very well. Roger's project, the DoppleScAnt, uses eight 1/4- vertical whips arranged in a circular pattern. Only one antenna at a time is electrically selected.
Figure 2 Block Diagram of the WA2EBY Doppler RDF System Antenna Switcher 1 of 4 Data Selector Ant 8 KHz Clock LED Compass Display 1 of 16 Data Selector Binary Counter Latch High Pass Filter Low Pass Filter Digital Filter Zero Crossing Detector Adjustable Delay AF Out R 36 Calibrate FM Receiver External Speaker shown in figure 1.
Three Synchronized Functions The first function derived from binary counter U7 is antenna array spinning. This is accomplished by using the two most significant bits of U7 to run 1 of 4 multiplexer U8. The selected output of U8 (active low) is inverted by buffer U12. The buffered output of U12 (active high) supplies current sufficient to turn on the antenna to which it is connected. (The details of how this is done will be covered later.) Buffer outputs U12A, U12B, U12C and U12D are sequenced in order.
truly an elegant feature of the Doppler RDF design. Using the same clock oscillator to spin the antenna and clock the digital filter ensures the Doppler tone produced by the spinning process is precisely the center frequency of the digital filter. Even if the clock oscillator frequency drifts, the Doppler tone drifts accordingly, but the center frequency of the digital filter follows it precisely because the same clock runs it.
divider, R21 and R22. U2D's output remains high when the Doppler tone is present and above 0.11 V peak. C9 discharges via D2 whenever U2D goes low, causing U3's output (pin 7) to go high, turning on Q2 via R24 and illuminating low signal level LED, D4. D4 remains on until the Doppler tone returns with amplitude above 0.11 V peak and C9 recharges via R23. The LED display remains locked by disabling U11's strobe input whenever the Doppler tone is too low for an accurate bearing.
DDF1 PARTS LIST Sort and “check off” the components in the boxes provided. It’s also helpful to sort the parts into separate containers (egg cartons do nicely) to avoid confusion while assembling the kit. Leave the IC’s on their foil holder until ready for installation. RESISTORS AND POTENTIOMETERS 2 2 4 1 7 1 2 1 18 1 2 1 3 1 2 47 ohm (yellow-violet-black) [R42,51] 330 ohm (orange-orange-brown) [R17,25] 470 ohm (yellow-violet-brown) [R46,47,48,49] 3.
SEMICONDUCTORS AND INTEGRATED CIRCUITS 11 1N4148 small signal diode (small glass case with banded end) [DDF1 board D1,2,5 ANTINT-1 board D1,2,3,4 ANTMTG-1 board 1 ea.
RAMSEY Learn-As-You-Build KIT ASSEMBLY There are numerous solder connections on the DDF1 printed circuit board. Therefore, PLEASE take us seriously when we say that good soldering is essential to the proper operation of your direction finder! • • • • Use a 25-watt soldering pencil with a clean, sharp tip. Use only rosin-core solder intended for electronics use. Use bright lighting, a magnifying lamp or bench-style magnifier may be helpful. Do your work in stages, taking breaks to check your work.
DDF1 DOPPLER DIRECTION FINDER ASSEMBLY STEPS Although we know that you are anxious to complete the assembly of your direction finder finder kit, it will become necessary to assemble in a specific order to accomplish the final components installation of your unit. Try to avoid the urge to “jump ahead” installing components. Please also note that the components will mount on BOTH SIDES OF THE PRINTED CIRCUIT BOARD for proper alignment into the provided case assembly.
sure all 8 pins are through the board before soldering the IC in place. This IC is responsible for the master clock oscillator for the direction finder unit , and replaces a few dozen discreet components. 5. Install C24, .001uF disc capacitor (marked 102). 6. Install R29, 68K ohm (blue-gray-orange). 7. Install R28, 18K ohm (brown-gray-orange). 8. Install C26, .001uF disc capacitor (marked 102). 9. Install R27, 10K ohm (brown-black-orange). 10. Install R26, 33K ohm (orange-orange-orange). 11.
noting the cathode (negative) side of the diode. Install as shown in the parts placement diagram (D6 is adjacent to the power switch S1). 19. Moving again towards the lower right of the main circuit board (component side view), find the position for U6, the other 555 timer IC. Install U6, the 555 timer IC. Make sure to align the notch or dot associated with pin one with the notch shown in the parts layout diagram. 20. Install R34, 33K ohm (orange-orange-orange). 21.
DDF-1 MAIN BOARD PARTS LAYOUT DIAGRAM DDF1 • 17
DDF1 • 18
DDF1 • 19
32. Install U11, the 24 pin 74HC4515 IC. Make sure all the pins pass through the circuit board before e soldering. Great job so far! Take a moment now to check your previous solder joints for “opens” where the solder did not completely flow around the connection or solder “bridges” between closely spaced pads or IC pins. It seems the best time to identify these types of problems is now when you’re focused on this section of the board, saving you time to try to rethink your steps later. 33.
that electrolytics are polarized and must be mounted as shown in the diagram. 47. Install U3, the 324 op amp. Be sure to point the dot, notch, or band as shown in the parts diagram. Solder all 14 leads 48. Install R15, 220K ohm (red-red-yellow). 49. Install R17, 330 ohm (orange-orange-brown). 50. Moving to the right of J3, Install R43 and 45, both 33K ohm (orangeorange-orange). 51. Install transistor Q1, a 2N3904 type (marked 3904). Be sure to orient the flat side as shown in the parts diagram.
64. Install a 324 Op amp in the U1 position, paying attention to the correct part placement. Solder all 14 pins. 65. Install R9 and R10, both 33K ohm (orange-orange-orange). 66. Install R1, 33K ohm (orange-orange-orange). 67. Install R4, 27K ohm (red-violet-orange). 68. Install C1, .01uF (marked .01 or 103 or 10nF) . 69. Install R2,R3, and R7, all 33K ohm (orange-orange-orange). 70. Install C2 and C3, both .01uF (marked .01 or 103 or 10nF). Great going! You are really making progress now.
Whew! Well, that's about it for the main circuit board assembly. Take a few minutes now to double check your work, especially the placement of the polarized and orientation specific components. The next time we re-visit this board we’ll be ready to energize the circuit, so this is your last chance to “get it right the first time” and avoid timely circuit troubleshooting. Remember that time spent here can save a lot of time (and expense!) when the unit is initially turned on.
how one lead is longer than the other. The longer of the two leads is the anode, or (+) connection. Most diodes also have a flat molded in the component body. This corresponds to the cathode or (-) side of the part. Note also that while both of the holes is rectangular, only one of the holes has the corners “rounded off“. The longer (anode) lead belongs in the “rounded off” hole, and the shorter (cathode) lead belongs in the rectangular (non-rounded) hole.
Use the shortest lead length possible. Note that these components are polarized. Install the banded end as shown in the parts diagram. Don’t worry about too much heat from your soldering iron; you will not damage the diodes. 2. In the same manner form and install inductors L1, 2, 3, and 4 (brown-red-gold). Keep those lead lengths as short as possible. 3. There are also eight .001uF disc capacitors to be installed. Again, see the diagram for proper placement.
2. “Prep” each of the coaxial cables as shown in the diagram. Be careful not to use too much heat when “tinning” the braid of the coax as this could damage the center insulating shield. 3. Using some of your longer scrap resistor leads bent into a “U” shape, hold the coax into position and slide the “jumpers” through the provided mounting holes. These “jumpers” can be soldered on the bottom side of the board to hold the coax into position for final soldering. 4.
FINAL ASSEMBLY Our last task is to mount the antenna switcher cable to the ANTINT circuit board. Special care must be used to ensure that the antennas sequence in the correct order for proper operation of the RDF unit. You can use any type of 5 conductor wire; 4 pair telephone wire or computer LAN cable works well. If you look closely at the male DB9 connector provided with your kit you will see that each of the pins is numbered. Solder one end of each of your 5 wires to the pins numbered 1 through 5.
ms (8 kHz). Use a frequency counter to verify the clock frequency is 8 kHz +/- 250 Hz if you desire. Getting the clock frequency to exactly 8 kHz is not necessary for proper operation, however, the values of R27 and R28 can be changed to adjust the clock frequency. Verify that closing switch S2 disables the clock. Open S2 (scan stop) and verify the operation of BCD counter U7 by connecting the oscilloscope sequentially to pins 14,13,12, and 11.
Direction Indicator Adjust the frequency of the audio generator very slowly around 500 Hz while observing the LED display. You should see the direction indicating LEDs around the green center LED illuminating. The LED illumination should rotate clockwise when the frequency of the generator is set slightly lower than the antenna rotation frequency. (Only one LED will be on when the frequency of the generator equals the antenna rotation frequency.) The display should rotate counterclockwise.
Scan/stop switch S2 stops the antenna from spinning. Close and open S2 until the voltage on terminal J2 pin 1 reads +5V. Pins 2, 3 and 4 should all read 0V. Pin 1 is the antenna enable signal for antenna 1. Label the corresponding mag mount antenna on the table as antenna 1. Close and open S2 until the voltage on terminal J2 pin 2 reads +5V. Pins 1,3, and 4 should all read 0V.
also work well. As a safety measure, secure each PopTop Mag-Mount with 20 pound fishing line when operating the vehicle at highway speeds. Attach all four whip antennas to the mag-mount antenna bases placed about the center of the car top. Connect the RF output of the antenna switcher to a FM receiver transceiver tuned to a strong NOAA weather broadcast signal.
Those signal components may arrive from different directions causing false bearing indications. The LED display tends to jump around randomly under these conditions. Avoid taking bearing information when the Doppler tone sounds raspy. You can minimize display jitter by slowing the response time of the digital filter. This is accomplished by increasing damping control R19. With a little time, you can master the art of Doppler RDFing.
speaker into the 2 pin header and align the case top and bottom. Put a few more screws in place and you’re ready to roll. TROUBLESHOOTING INSTRUCTIONS While we had hoped that it wouldn’t come to this, if you are having trouble with your direction finder, here are a few suggestions. Use a methodical, logical troubleshooting technique. Most problems can be solved using common sense. A volt-ohm meter and a clear head are usually all that are needed to correct any problem.
DDF-1 ANTENNA SCHEMATIC DIAGRAM DDF1 • 34
The Ramsey Kit Warranty Please read carefully BEFORE calling or writing in about your kit. Most problems can be solved without contacting the factory. Notice that this is not a "fine print" warranty. We want you to understand your rights and ours too! All Ramsey kits will work if assembled properly. The very fact that your kit includes this new manual is your assurance that a team of knowledgeable people have field-tested several "copies" of this kit straight from the Ramsey Inventory.
Doppler Radio Direction Finder Quick Reference Page Guide Introduction to the DDF1................ 4 DDF1 Circuit Description ............... 4 Parts List .......................................11 DDF1 Assembly Steps..................14 Component Layout .......................17 Schematic Diagram ......................18 Initial Testing.................................22 Ramsey Warranty .........................
